It is known that modern engines are provided with a fuel injection system for directly injecting the fuel into the cylinders of the engine. The fuel injection system generally comprises a fuel common rail, which is kept under high pressure by a high pressure pump and electrically controlled fuel injectors, which are individually located in a respective cylinder of the engine and are hydraulically connected to the fuel common rail through dedicated injection lines. Each fuel injector generally comprises a nozzle and a movable needle that repeatedly opens and closes this nozzle; fuel can thus be injected into the cylinder giving rise to single or multi-injection patterns at each engine cycle.
The needle is moved with the aid of a dedicated actuator, typically a solenoidal actuator or a piezoelectric actuator, which is controlled by an engine control unit (ECU). The ECU operates each fuel injection by generating an electric opening command, causing the actuator to open the fuel injector nozzle for a predetermined amount of time, and a subsequent electric closing command, causing the actuator to close the fuel injector nozzle. The time between the electric opening command and the electric closing command is generally referred as energizing time of the fuel injector, and it is determined by the ECU as a function of a desired quantity of fuel to be injected.
During normal use of the vehicle it may happen that the user notices some anomalies in the functioning of the engine, for example an excessively noisy engine or an engine that does not respond adequately to the driver's input, leading to drivability problems, namely to a degrading of the smoothness and steadiness of acceleration of an automotive vehicle or other undesired degradation of engine's performance such as excessive emissions. A possible cause of these phenomena is the clogging of one or more injector in the engine due, for example, to coking presence.
At least one object is to provide a test procedure that can be performed at a vehicle service center to verify if one or more injectors are clogged or partially clogged. At least a further object is to provide an injector clogging detection procedure while avoiding engine shutdown, even in case of big engines having a high number of cylinders. Yet still another object is to provide a procedure that can be used to identify a clogged injector for repair or substitution in order to avoid emission increase due to anomalous engine performance. At least another object is to provide such detection without using complex devices and by taking advantage from the computational capabilities of the Electronic Control Unit (ECU) of the vehicle. In addition, other objects, desirable features, and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.